for Journals by Title or ISSN
for Articles by Keywords
help
Followed Journals
Journal you Follow: 0
 
Sign Up to follow journals, search in your chosen journals and, optionally, receive Email Alerts when new issues of your Followed Journals are published.
Already have an account? Sign In to see the journals you follow.
Journal Cover Composites Science and Technology
  [SJR: 1.512]   [H-I: 144]   [177 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0266-3538
   Published by Elsevier Homepage  [3043 journals]
  • A micro-image based reconstructed finite element model of needle-punched
           C/C composite
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Jian Yu, Chuwei Zhou, Haijun Zhang
      A 3D microscopic FE approach of needle-punched carbon-carbon composite (NP C/C) is modeled based upon micro-CT technology. The images of micro-CT of NP C/C are processed and the outlines of warp, weft and punched fibre bundles are extracted. Then discrete gray images are generated and from them a microscopic FE model is reconstructed which can represent the features of micro structure and imperfections in NP C/C. Failure criterion and periodic boundary condition are employed in the FE approach and then progressive damages are investigated. Numerical simulation reveals the predominant failure mechanisms in this NP C/C under uniaxial tensile and compressive loads. The predicted stress/strain curves agree well with the experiment data.

      PubDate: 2017-10-14T01:51:33Z
       
  • Modelling hybrid effects on the stiffness of aligned discontinuous
           composites with hybrid fibre-types
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): J. Henry, S. Pimenta
      Hybrid discontinuous composites offer the possibility to tailor the composite properties for specific applications, improve their manufacturability, and reduce cost by introducing cheaper fibres. However, the mechanical behaviour of hybrid composites often shows hybrid effects which cannot be modelled by the rule-of-mixtures and are therefore challenging to predict and explain. This paper presents models to calculate the Young's modulus of different discontinuous hybrid composites, which is affected by such hybrid effects. The models are based on shear-lag and consider two types of hybrid discontinuous architectures: (i) a deterministic “brick-and-mortar” architecture consisting of perfectly staggered platelets with two different Young's moduli and thicknesses, and (ii) a stochastic architecture of aligned fibres with two different Young's moduli and diameters, with randomly allocated fibre-ends and random or organised intermingling. The models show good agreement with numerical and experimental validations; their results show that hybrid interactions between different types of fibres or platelets reduce the Young's modulus of hybrid discontinuous composites, which justifies the negative hybrid effects observed.

      PubDate: 2017-10-14T01:51:33Z
       
  • A micromechanical model of interfacial debonding and elementary fiber
           pull-out for sisal fiber-reinforced composites
    • Abstract: Publication date: Available online 12 October 2017
      Source:Composites Science and Technology
      Author(s): Qian Li, Yan Li, Limin Zhou
      The interfacial failure behavior of sisal fiber-reinforced composites (SFRCs) was studied experimentally and theoretically. The residual pull-out strength of the SFRCs was observed to gradually decrease during the single sisal fiber pull-out test, after which the SFRCs presented multiple failure modes, including at the interface between technical fiber and matrix and at the interface between elementary fibers. To further investigate the failure mechanisms of SFRCs, using the traditional shear lag model, a double-interface model tailored to the unique multi-layer interface structure of plant fibers was developed to describe the fiber pull-out behavior and the interfacial adhesion status of single plant fiber-reinforced composites (PFRCs). By comparison with other existing models, using the experimental applied stress as reference, the proposed double-interface model was found to provide a more accurate quantitative theoretical prediction of the interfacial failure behavior of PFRCs during multi-stage fracture of the two interfaces.

      PubDate: 2017-10-14T01:51:33Z
       
  • A flexible and transparent thin film heater based on a carbon fiber
           /heat-resistant cellulose composite
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Pengbo Lu, Fan Cheng, Yanghao Ou, Meiyan Lin, Lingfeng Su, Size Chen, Xilang Yao, Detao Liu
      The thin flexible film heater made of carbon fibers is widely considered to be an ideal material for the use as self-heating devices because of its safe, low-cost, no noises, small size and fast heating as well as energy saving. Presently thin flexible film heater is mostly fabricated by mixing method using the long cellulose fibers as film-forming materials and carbon fibers as self-heating materials, which mostly suffer from opaque or uneven heating field. In this work, we firstly reported a flexible and transparent thin film heater (FTFH) composed of carbon fibers and regenerated cellulose. The use of regenerated cellulose for membrane materials brings high transmittance, strong adhesion, fast temperature response and high generated temperature. More importantly, the FTFH using novel carbon fibers as self-heating materials and regenerated cellulose as membrane materials show a rapid heating response (12 s), higher power density (2577 w/m2) and long-term stability of generated temperature (162.3 °C).

      PubDate: 2017-10-11T01:48:13Z
       
  • Multi-scaled carbon reinforcements in ternary epoxy composite materials:
           Dispersion and electrical impedance study
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): D. Baltzis, D.G. Bekas, G. Tzachristas, A. Parlamas, M. Karabela, N.E. Zafeiropoulos, A.S. Paipetis
      The following study, is focused on developing a ternary epoxy based composite material by the combined inclusion of two types of carbon fillers. The selected fillers (i.e. multi-walled carbon nano-tubes, MWCNTs and carbon black, CB), were dispersed using high speed shear mixing while the effect of dispersion duration, filler type and weight contents was studied using Impedance Spectroscopy (IS), fracture toughness tests and Dynamic Mechanical Thermal Analysis (DMTA). SEM was also employed in order to qualitatively assess the dispersion quality by means of mean agglomerate size and identify the fracture mechanisms. IS results indicated an inverse dependence between the magnitude of impedance and the dispersion duration. The decrease of the impedance with increasing dispersion duration was attributed to the formation of the conductive network. The synergistic effect between the two fillers was evident in the more rapid decrease in the maximum imaginary impedance values followed by a concurrent shift of the observed peaks towards higher frequencies with increasing dispersion duration. The synergy of the two fillers was also evident in the superior fracture toughness and thermomechanical performance of the ternary composites. The SEM micrographs revealed that the fracture surfaces of the ternary composites combined all the fracture mechanisms observed on the respective binary composites i.e. particle pull-out, crack bifurcation and pinning. DMTA revealed a significant increase in the storage modulus while glass transition temperature was marginally affected. Overall, the formation of the hybrid conductive network resulted in ternary composite materials with improved electric, mechanical and thermomechanical performance.
      Graphical abstract image

      PubDate: 2017-10-11T01:48:13Z
       
  • A micro-scale cutting model for UD CFRP composites with thermo-mechanical
           coupling
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Hui Cheng, Jiaying Gao, Orion Landauer Kafka, Kaifu Zhang, Bin Luo, Wing Kam Liu
      Cutting a unidirectional carbon fiber-reinforced polymer (UD CFRP) structure is the basic unit for CFRP machining, which is a complex thermal-mechanically coupled process. To reveal the deformation mechanism and predict cutting force in UD CFRP micro cutting, a micro-scale fracture model for UD CFRP cutting with thermal-mechanical coupling is demonstrated in this paper, which captures the failure modes for fibers, matrix and the interface based on a micro-level RVE using a relatively simple damage-based fracture method. The thermal-mechanical coupling model at the micro scale is developed on the basis of the plastic energy dissipation and frictional heating during cutting. Failure models for the fiber, matrix and interface region are applied depending on the material properties of each of these three phases. Numerical simulations based on the above model with different fiber orientations were performed to predict the deformation and forces of different components in UD CFRP. Cutting experiments with the same fiber orientations as considered in the simulations were carried out to validate the force and deformation results. The predicted force and deformation patterns match well with evidence from our experiments. In general, the cutting force is larger than the thrust force regardless of fiber orientation. The cutting force reaches a maximum as the fiber orientation approaches 90°, but thrust forces do not vary substantially across cases. When the fiber orientation is acute, the deformation of fibers is much smaller than when the cutting angle is obtuse. Surface roughness follows the same trend with cutting angle as fiber deformation.

      PubDate: 2017-10-11T01:48:13Z
       
  • A facile preparation route of n-type carbon buckypaper and its enhanced
           thermoelectric performance
    • Abstract: Publication date: 1 December 2017
      Source:Composites Science and Technology, Volume 153
      Author(s): Jinmi Kim, O Hwan Kwon, Young Hun Kang, Kwang-Suk Jang, Song Yun Cho, Youngjae Yoo
      In this study, we prepared a thermoelectric device with p-type organic thermoelectric hybrid film and n-type buckypaper. Both the film and buckypaper are made of a hybrid filler of graphite nanoplatelets (GNPs) and single-walled carbon nanotubes (SWNTs). The p-type thermoelectric hybrid film has a free-standing form and enhanced thermoelectric performance owing to a polyvinylidene fluoride/carbon hybrid film purified with an acid solution, which successfully eliminates amorphous carbon, additives, and impurities. The n-type thermoelectric buckypaper was made with a filtration method with GNPs and SWNTs to the membrane filter. To convert this to an n-type thermoelectric property, a polyethyleneimine solution was also added by filtration process. In addition, adding sodium dodecyl benzene sulfonate during carbon dispersion enhanced thermoelectric performance, which was confirmed by measuring the electrical conductivity and Seebeck coefficient. A thermoelectric device using silver electrodes was produced with the thermoelectric composite film and buckypaper to verify its thermoelectric voltage and generating power.

      PubDate: 2017-10-11T01:48:13Z
       
  • Dielectric behavior and electrical conductivity of PVDF filled with
           functionalized single-walled carbon nanotubes
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): J.A. Puértolas, J.F. García-García, F.J. Pascual, J.M. González-Domínguez, M.T. Martínez, A. Ansón-Casaos
      Polyvinylidene fluoride (PVDF)/single-walled carbon nanotube (SWCNT) composites are characterized by X-ray diffraction and scanning calorimetry, and studied by dielectric relaxation spectroscopy (DRS) in the temperature range of −75 to 150 °C. The effects of SWCNTs and SWCNT functionalization are analyzed in terms of α and αc relaxation, dielectric permittivity, loss tangent, and AC electrical conductivity. Some small changes are detected in α relaxation with the addition of SWCNTs, and a strong influence of SWCNTs is observed in the other relaxation αc. Below the percolation threshold, the dielectric permittivity of functionalized SWCNT composites increases compared to blank PVDF, without notable changes in the dielectric loss. All the composite systems show an electrical percolation behavior with different thresholds depending on SWCNT functionalization. Threshold concentrations remain nearly unchanged in the whole temperature and frequency ranges. The base PVDF conductivity strongly depends on temperature and frequency, while the maximum conductivity above the percolation remains nearly unchanged (∼10−2 S/m) for all the systems, temperatures and frequencies.

      PubDate: 2017-10-11T01:48:13Z
       
  • A simple model for electrical conductivity of polymer carbon nanotubes
           nanocomposites assuming the filler properties, interphase dimension,
           network level, interfacial tension and tunneling distance
    • Abstract: Publication date: Available online 10 October 2017
      Source:Composites Science and Technology
      Author(s): Yasser Zare, Kyong Yop Rhee
      This manuscript proposes a simple model for electrical conductivity of polymer carbon nanotubes (CNT) nanocomposites including the crucial parameters such as the volume fraction, effective volume fraction, percolation threshold, dimensions, waviness and conduction of CNT, interphase thickness, network fraction, interfacial tension between polymer and nanoparticles and tunneling distance between adjacent CNT. The proposed model is verified by the experimental data from various samples. Furthermore, the dependence of predicted conductivity on the model parameters is determined and discussed to approve the proposed model. The calculations of the proposed model successfully agree with the experimental conductivity data in the reported samples. In addition, the model parameters demonstrate acceptable effects on the conductivity. Some parameters such as filler volume fraction, tunneling distance, network fraction and interfacial tension meaningfully affect the conductivity of nanocomposites. On the contrary, the dimensions, conduction and percolation threshold of CNT insignificantly change the conductivity.

      PubDate: 2017-10-11T01:48:13Z
       
  • Polymer/carbon nanotube composite materials for flexible thermoelectric
           power generator
    • Abstract: Publication date: Available online 9 October 2017
      Source:Composites Science and Technology
      Author(s): Haijun Song, Yang Qiu, Yao Wang, Kefeng Cai, Delong Li, Yuan Deng, Jiaqing He
      Flexible and lightweight thermoelectric (TE) generators have attracted increasing interest for powering wearable electronics using the temperature difference between human body and ambient air. Conducting polymers or their based composite materials are suitable for such applications; however, most conducting polymers show p-type conduction, hence, until now almost all reported flexible TE generators, which use conducting polymers or their based composite materials, are single-carrier-type (p-type) leg devices, connecting alternatively p-type legs electrically in series with silver or other metals. In this paper, both p- and n-type flexible TE materials have been developed using polymers and single-walled carbon nanotubes (SWCNTs). The p-type TE films are prepared by integrating SWCNTs into a high conductive poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) matrix, using a dilution-filtration method. N-type TE films with Seebeck coefficient about -35 μV/K are realized by treating SWCNTs with polyethyleneimine (PEI), and an encapsulation process has been employed to effectively preserve its n-type characteristics. Benefited from the flexibility of both the substrate and the composite films, a flexible TE prototype composed of six p-n junctions connected in series has been fabricated to demonstrate TE voltage output and power generation. The output power from the prototype is 220 nW for a 50 K temperature gradient.
      Graphical abstract image

      PubDate: 2017-10-11T01:48:13Z
       
  • Electric field assisted gradient structure formation of glass microsphere
           columns in polymer films
    • Abstract: Publication date: Available online 7 October 2017
      Source:Composites Science and Technology
      Author(s): Xueqing Liu, Jiyan Liu, Yuanhao Guo, Miko Cakmak
      Electric field-driven fabrication of gradient particle/polymer film was presented in current work. Direct-current (DC) field drives hollow glass microspheres (HGMs) to form microcolumns in UV-curable resin NOA65 by electrophoresis force and subsequently cured. In this field assisted alignment process, the microcolumns also exhibit gradient structure. The real-time organization of HGMs in the NOA65 was monitored during DC application by measuring the light transmission and taking photos with visible spectrometers and optical microscope respectively as the formation of column formation creates depletion zones between the columns leading to higher light transmission. The morphology evolved was found to depend on the electric field strength used and exposure time. The mechanical properties of the films produced by this process exhibit unique anisotropies when tested parallel and perpendicular to the electric field. When 10 phr HGMs in NOA65 undergoes 1000V/mm of DC for 0, 2, 4, 8 min respectively, the film obtained at 8 min shows highest storage modulus while the film obtained at 4 min shows highest modulus in compression mode.

      PubDate: 2017-10-11T01:48:13Z
       
  • Suppression of elevated temperatures space charge accumulation in
           polypropylene/elastomer blends by deep traps induced by surface-modified
           ZnO nanoparticles
    • Abstract: Publication date: Available online 7 October 2017
      Source:Composites Science and Technology
      Author(s): Bin Dang, Qi Li, Yao Zhou, Jun Hu, Jinliang He
      Space charge accumulation is a critical issue for the deterioration of the elevated temperature insulating property of polymeric materials. We present the influence of surface-modified ZnO nanoparticles on the space charge distribution and direct current (DC) resistivity of polypropylene (PP)/elastomer blends under elevated temperature. Octyltrimethoxysilane, a silane coupling agent, was used for the surface modification of nanoparticles. Morphology characterization results indicated that the elastomer and coated ZnO were well dispersed in the PP matrix. It was observed that the coated ZnO can significantly improve the insulating properties, including a minimized electric field distortion (4.0%) and increased DC volume resistivity (1.41 × 1018 Ω m) under an electric field of 40 kV/mm and 70 °C. The DC resistivity of 2 ph PP/elastomer/ZnO ternary composites was improved by 13.4 times compared with that of pure PP/elastomer blends. The suppression of space charges may originate from deep traps existing in spherulite boundaries and interfacial zones between polypropylene and ZnO. This work provides an effective method to endow a recyclable insulating material with outstanding elevated temperature insulating performances.

      PubDate: 2017-10-11T01:48:13Z
       
  • Preparation of NBR/Tannic acid composites by assembling a weak IPN
           structure
    • Abstract: Publication date: Available online 6 October 2017
      Source:Composites Science and Technology
      Author(s): Shuyan Yang, Wenjian Wu, Yuanqi Jiao, Zhuodi Cai, Hongbo Fan
      Sustainable self-reinforcement organic filler, which does not contribute to environmental pollution, has been realized in the rubber industry as an alternative to modifying inorganic fillers with coupling agents or preparing rubber fillers, such as carbon black, with petrochemical products that cause environmental problems. In this work, tannic acid (TA), the world's third largest class of plant components that are easily available, is used as a self-reinforcing organic filler to prepare nitrile–butadiene rubber/TA (NBR/T) composites. Results show that TA can melt partially under vulcanization to assemble a weak interpenetrating polymer network (IPN) structure by hydrogen bonds under cooling, which is responsible for the dramatic increase in the mechanical and flexible properties of NBR/T composites even at low TA dosage. This finding provides a new perspective in preparing high-performance and sustainable rubber composites without sacrificing fossil fuels or non-renewable environmental resources.

      PubDate: 2017-10-11T01:48:13Z
       
  • The combination of π-π interaction and covalent bonding can
           synergistically strengthen the flexible electrical insulating
           nanocomposites with well adhesive properties and thermal conductivity
    • Abstract: Publication date: Available online 6 October 2017
      Source:Composites Science and Technology
      Author(s): Zheng Su, Hua Wang, Konghu Tian, Weiqi Huang, Chao Xiao, Yulan Guo, Jing He, Xingyou Tian
      Adding thermal conductive filler is an effective method to improve the thermal conductivity of polymer matrix. In this research, we demonstrated that the polymer composites with much improved thermal conductivity while maintaining low electrical conductivity, which could be achieved via using hybrid 2D stacked filler and controlling the alignment of the filler in polymer matrix. In order to do this, the graphene oxide (GO) was prepared and simultaneously reduced/functionalized by diethylenetriamine (DETA) to obtain NH2-functionalized graphene (NfG) which designed to be immobilized on the surface of large-sized insulating hexagonal boron nitride (h-BN) via π-π stacking interaction. In this situation, since the NfG sheets were fixed on the surface of h-BN, the NfG sheets were well separated from each other and participated in the resin curing process. Hence, not only significantly enhanced thermal conductivity (∼3.409 W/m·K, in-plane direction) was obtained, but also a very low electrical conductivity was achieved. The low electrical conductivity was believed to be ascribed to both embedded insulating network of h-BN to inhibit the mobility of charge carrier and well-separated NfG sheets via π-π stacking interaction. In addition, the nanocomposites also exhibited good thermal stability and adhesive properties. We believed that this special structure will provide a new thought for fabricating thermal interface materials (TIMs) with much high thermal conductivity as well as low electrical conductivity.

      PubDate: 2017-10-11T01:48:13Z
       
  • Assessing local yield stress and fracture toughness of carbon nanotube
           poly(methyl methacrylate) composite by nanosectioning
    • Abstract: Publication date: Available online 4 October 2017
      Source:Composites Science and Technology
      Author(s): F. Sun, U. Wiklund, F. Avilés, E.K. Gamstedt
      A nanosectioning (cutting) method was used to test the local shear yield stress and fracture toughness (specific work of surface formation) of multiwall carbon nanotube (MWCNT) poly(methyl methacrylate) (PMMA) composites, and the effect of MWCNT content on the stress and toughness were investigated. The composites were prepared by a solution casting method, with MWCNT content varying from 0.05 to 1.0 wt%. Above 0.1 wt% MWCNT content, the yield stress reduced by the addition of MWCNTs. The fracture toughness of the composite was effectively enhanced by the addition of MWCNTs, from 17 J/m2 for the neat PMMA to 25 J/m2 for the 1.0 wt% composite. The shear yield stresses obtained by nanosectioning were correlated to nanoindentation measurement, and possible contributions from the MWCNTs to the fracture toughness of the composite were analysed.

      PubDate: 2017-10-11T01:48:13Z
       
  • Wet and dry flexural high cycle fatigue behaviour of fully bioresorbable
           glass fibre composites: In-situ polymerisation versus laminate stacking
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Menghao Chen, Jiawa Lu, Reda M. Felfel, Andrew J. Parsons, Derek J. Irvine, Christopher D. Rudd, Ifty Ahmed
      Fully bioresorbable phosphate based glass fibre reinforced polycaprolactone (PCL/PGF) composites are potentially excellent candidates to address current issues experienced with use of metal implants for hard tissue repair, such as stress shielding effects. It is therefore essential to investigate these materials under representative loading cases and to understand their fatigue behaviour (wet and dry) in order to predict their lifetime in service and their likely mechanisms of failure. This paper investigated the dry and wet flexural fatigue behaviour of PCL/PGF composites with 35% and 50% fibre volume fraction (Vf). Significantly longer flexural fatigue life (p < 0.0001) and superior fatigue damage resistance were observed for In-situ Polymerised (ISP) composites as compared to the Laminate Stacking (LS) composites in both dry and wet conditions, indicating that the ISP promoted considerably stronger interfacial bonding than the LS. Immersion in fluid (wet) during the flexural fatigue tests resulted in significant reduction (p < 0.0001) in the composites fatigue life, earlier onset of fatigue damage and faster damage propagation. Regardless of testing conditions, increasing fibre content led to shorter fatigue life for the PCL/PGF composites. Meanwhile, immersion in degradation media caused softening of both LS and ISP composites during the fatigue tests, which led to a more ductile failure mode. Among all the composites that were investigated, ISP35 (35% Vf) composites maintained at least 50% of their initial stiffness at the end of fatigue tests in both conditions, which is comparable to the flexural properties of human cortical bones. Consequently, ISP composites with 35% Vf maintained at least 50% of its flexural properties after the fatigue failure, which the mechanical retentions were well matched with the properties of human cortical bones.
      Graphical abstract image

      PubDate: 2017-10-11T01:48:13Z
       
  • Enhancing the neutron shielding ability of polyethylene composites with an
           alternating multi-layered structure
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Xianlong Zhang, Mingtao Yang, Xiaomeng Zhang, Hong Wu, Shaoyun Guo, Yuzhong Wang
      Neutron radiation is often encountered in a wide range of industries, such as aerospace, healthcare and nuclear power plants. It has been an arduous challenge to shield this neutron radiation to improve equipment safety and protect human health. In order to make an effective neutron shielding material, alternating multi-layered composites (high density polyethylene)/(high density polyethylene/boron nitride), (HDPE/(HDPE/BN)) and (HDPE/BN)/(HDPE/Barium sulfate (BaSO4)) were fabricated using a multi-layered co-extrusion system. The HDPE/BN layers in the alternating multilayered HDPE/(HDPE/BN) and (HDPE/BN)/(HDPE/BaSO4) composites had a continuous and layered distribution in their structure, with the BN particles oriented in the extrusion direction. The probability of collision between incident photons and flake-shaped particles is enhanced through alignment of the oriented BN particles. In this way, neutron transmittance noticeably decreased with an increasing number of layers. Compared to traditional polymer-blended materials, the alternating multilayered composites showed excellent shielding efficiency. In addition, the results of the dynamic rheological analysis showed that alternating multi-layered composites with more layers can weaken the cross-linking effects induced by secondary radiation. Furthermore, according to the Nano-TA analysis, BaSO4 was an effective shield of secondary radiation, so the average melting point, in nanoscale, can be represented as follows: (Nano- T m ¯ ) ((HDPE/BN)/(HDPE/BaSO4)) > Nano- T m ¯ (HDPE/(HDPE/BN)).

      PubDate: 2017-10-11T01:48:13Z
       
  • Electrical conductivity and mechanical properties of melt-spun ternary
           composites comprising PMMA, carbon fibers and carbon black
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Muchao Qu, Fritjof Nilsson, Yijing Qin, Guanda Yang, Yamin Pan, Xianhu Liu, Gabriel Hernandez Rodriguez, Jianfan Chen, Chunhua Zhang, Dirk W. Schubert
      In this study, the electrical conductivity of melt spun composites consisting of PMMA containing both aligned carbon fibers (CF) and carbon black (CB) has been investigated. A broad range of composite compositions (up to 50 vol % CF and 20 vol % CB) was studied. The percolation thresholds of binary PMMA/CF and PMMA/CB composites were determined to 31.8 and 3.9 vol %, respectively. Experimental conductivity contour plots for PMMA/CF/CB ternary composites were presented for the first time. Additionally, based on a model for predicting the percolation threshold of ternary composites, a novel equation was proposed to predict the conductivity of ternary composites, showing results in agreement with corresponding experimental data. Finally, two mechanical contour plots for elastic modulus and tensile strength were presented, showing how the decreasing tensile strength and increasing E-modulus of the PMMA/CF/CB ternary composites was depending on the CB and CF filling fractions. The systematic measurements and novel equations presented in this work are especially valuable when designing ternary conductive polymer composites with two different fillers.

      PubDate: 2017-10-11T01:48:13Z
       
  • Damage and failure of triaxial braided composites under multi-axial stress
           states
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Tobias Wehrkamp-Richter, Roland Hinterhölzl, Silvestre T. Pinho
      Damage and failure of triaxial braided composites under multi-axial stress states was investigated. In order to introduce different multi-axial stress states in the material, uni-axial tensile tests were performed at different off-axis orientations. Three braid architectures, comprising braiding angles of 30 ° , 45 ° and 60 ° were each loaded parallel to their axial, transverse and braid yarn direction. Digital image correlation measurement techniques were used to quantify the effects of the textile architecture and its heterogeneity on the strain field, to identify and locate constituent failure mechanisms and to investigate damage initiation and development. In order to identify the driving physical mechanisms behind the material non-linearity, the evolution of the damage variable and the accumulated inelastic strain was quantified using incremental loading/unloading experiments. A high-speed camera was employed in order to study the dynamic nature of catastrophic failure. The triaxial braids within this study exhibited severe non-linearities in the mechanical response before final failure as a result of extensive matrix cracking. While we found the underlying textile architecture to slightly reduce the elastic properties compared to equivalent tape laminates, it functions as a natural crack arresting grid. As a result of this mechanism, braids under certain load conditions were capable of withstanding a higher strain to failure, even if a large portion of the specimen surface was saturated with matrix cracks. The accompanying mechanical behaviour can be desirable in the design of crash absorbing or pseudo-ductile materials. An additional failure mode intrinsic to the textile architecture was encountered for loading in the heavily undulated braid yarn direction. Due to yarn straightening and out-of-plane movements, braided composites were found to fail as a result of large scale delaminations accompanied by progressive fibre bundle pull-out.

      PubDate: 2017-10-11T01:48:13Z
       
  • Silver nanowire/carbon nanotube/cellulose hybrid papers for electrically
           conductive and electromagnetic interference shielding elements
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Hyeong Yeol Choi, Tae-Won Lee, Sang-Eui Lee, JaeDeok Lim, Young Gyu Jeong
      We report the microstructures, electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness of a series of hybrid cellulose papers coated alternatively with silver nanowire (AgNW) and multi-walled carbon nanotube (MWCNT), which are fabricated by controlling the dip-coating sequence and cycle. SEM images and EDS data reveal that AgNWs and/or MWCNTs are sequentially coated on the surfaces of the cellulose papers with increasing the dip-coating cycle and the coating density of the particles decreases gradually in thickness direction of the papers. This result is supported by the anisotropic apparent electrical conductivity of AgNW/MWCNT/cellulose hybrid papers in in-plane and thickness directions. In addition, the apparent electrical conductivity of the hybrid papers in the in-plane direction increases significantly from 0.17–0.22 S/cm to 2.55–2.83 S/cm with increasing the coating cycle from 2 to 10, although it is higher for the hybrid cellulose papers with AgNW top-coating layers than the hybrid papers with MWCNT top-coating layers at the same coating cycle. This result indicates that a highly effective and conductive AgNW/MWCNT network is formed on the cellulose fibers in a layer-by-layer manner. For the hybrid papers with 2.55–2.83 S/cm, high EMI shielding effectiveness of ∼23.8 dB at 1 GHz is achieved.

      PubDate: 2017-10-11T01:48:13Z
       
  • Influence from defects of three-dimensional graphene network on
           photocatalytic performance of composite photocatalyst
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Bo Tang, Haiqun Chen, Yanfeng He, Zhengwei Wang, Jun Zhang, Jinping Wang
      Three-dimensional graphene networks (3DGN) with various defect densities prepared by chemical vapor deposition method are adopted to modify TiO2 for high photocatalytic performances. Based on the obtained decomposition rate constants of phenol and Rhodamine-B, the photocatalytic activities of the resulting composite photocatalysts are found closely related to the defect density of the adopted 3DGN, which is proven by the electron paramagnetic resonance spectroscopy and tunneling electron microscope. It is revealed that the surface defects of the 3DGN can play as active sites to effectively adsorb pollutants, which is the key premise for the following decomposition process. Moreover, these defects further play as a bridge to achieve a close contact between the 3DGN and TiO2, enhancing electron transport ability between them. By adopting the 3DGN with a moderate defect density, photocatalytic performance of the resulting photocatalyst is significantly enhanced under both UV- and visible-light illumination, demonstrating that optimizing the employed 3DGN is an effective approach to enhance the photocatalytic activity of TiO2.

      PubDate: 2017-10-11T01:48:13Z
       
  • Three-phase PANI@nano-Fe3O4@CFs heterostructure: Fabrication,
           characterization and investigation of microwave absorption and EMI
           shielding of PANI@nano-Fe3O4@CFs/epoxy hybrid composite
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Farid Movassagh-Alanagh, Aidin Bordbar-Khiabani, Amin Ahangari-Asl
      In this work, a three phase carbon fiber (CF)-based electromagnetic (EM) wave absorbing and EM interference (EMI) shielding heterostructure was fabricated through a layer by layer assembly. The nano-Fe3O4 particles were deposited on CFs via a modified multi-step electrophoretic deposition (EPD). The PANI@nano-Fe3O4@CFs heterostructures were prepared using an in situ polymerization process of polyaniline (PANI) on nano-Fe3O4@CFs in HCl solution. The results showed that the PANI@nano-Fe3O4@CFs mats with a layer by layer (LBL) assembly were successfully fabricated. The saturated magnetization (Ms) of the as-synthesized nano-Fe3O4 powder decreased from 72.612 to 8.934 emu/g for the nano-Fe3O4@CFs and from 8.934 to 0.191 emu/g for the PANI@nano-Fe3O4@CFs mats due to the reduction in the effective mass/volume percentage of nano-Fe3O4 particles in the composites. The fabricated epoxy-based hybrid composites filled with PANI@nano-Fe3O4@CFs segments exhibited both of the dielectric and magnetic losses at the 8.2–18 GHz frequency range. The composite containing 1 wt% of PANI@nano-Fe3O4@CFs with the thickness of 1.5 mm showed a maximum reflection loss (RL) value of −11.11 dB with an effective absorption bandwidth of about 6 GHz in the frequency range of 8.2–18 GHz. Also, the sample filled with 5 wt % of EM wave absorbing segments with the thickness of 3 mm demonstrated an EMI shielding effectiveness (SE) value of 29 dB at the same frequency range.

      PubDate: 2017-10-11T01:48:13Z
       
  • Enhanced alignment and mechanical properties through the use of
           hydroxyethyl cellulose in solvent-free native cellulose spun filaments
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Saleh Hooshmand, Yvonne Aitomäki, Linn Berglund, Aji P. Mathew, Kristiina Oksman
      In this study, the addition of hydroxyethyl cellulose (HEC) in cellulose nanofiber filaments is shown to improve the solvent-free processing and mechanical properties of these biobased fibers as well as their compatibility with epoxy. An aqueous dope of cellulose nanofiber (CNF) with HEC was spun and the resulting filaments cold-drawn. The HEC increased the wet strength of the dope allowing stable spinning of low concentrations of CNF. These lower concentrations promote nanofiber alignment which is further improved by cold-drawing. Alignment improves the modulus and strength and an increase of over 70% compared to the as-spun CNF only filaments was achieved. HEC also decreases hydrophilicity thus increasing slightly the interfacial shear strength of the filaments with epoxy resin. The result is continuous biobased fibers with improved epoxy compatibility that can be prepared in an upscalable and environmentally friendly way. Further optimization is expected to increase draw ratio and consequently mechanical properties.

      PubDate: 2017-10-11T01:48:13Z
       
  • Scale effect on tribo-mechanical behavior of vegetal fibers in reinforced
           bio-composite materials
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Faissal Chegdani, Mohamed El Mansori, Sabeur Mezghani, Alex Montagne
      The nature of friction of vegetal fiber and polymeric matrix in bio-composite materials is very important for many industrial applications. In order to design natural fiber composites for structural applications, the scientific understanding of tribo-mechanical phenomena inside the heterogeneous structure of natural fibers and also the overall heterogeneous structure of the bio-composite is required. This implies a special focus on the fundamental aspects of vegetal fiber friction at the macro-, meso-, and microscale. This research paper investigates the multiscale mechanical and friction properties of natural fibers. The mechanical properties of flax fibers, glass fibers (as a reference) and polypropylene matrix has been evaluated at microscale and mesoscale by Atomic Force Microscopy (AFM) and Nanoindenter XP (MTS Nano Instruments), respectively, using nanoindentation technique. At the macroscale, the mechanical behavior has been considered for the global composite structure. The micro-friction response of each composite component has been measured by instrumenting AFM for scratch test technique. The results show the scale dependence of mechanical behavior for flax fibers, unlike glass fibers and polypropylene matrix where their mechanical performances are independent of the analysis scale. Tribological results in terms of dynamic friction coefficient show that flax fibers induce more friction than glass fibers, while polypropylene matrix generates the highest friction. This is sign that vegetal fiber friction is scale dependent property as shown when referring to the contact mechanics theory. The arisen results are very important for many technical applications in PMCs surface engineering based on plant fibers.

      PubDate: 2017-10-11T01:48:13Z
       
  • Prediction and experiment on the compressive property of the sandwich
           structure with a chevron carbon-fibre-reinforced composite folded core
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Yuguo Sun, Yanxiao Li
      The compressive performances of carbon-fibre-reinforced composite sandwich panels with chevron folded cores were investigated in this paper. Analytical expression based on energy approach were derived to predict their compressive elastic modulus and strength. The sandwich panels with specific fibre orientation cores were manufactured and tested to reveal the influences of fibre ply angles on the responses for compressive loading. The stiffness and strength increased distinctly with the 0° fibre orientation increments. The predictions for compressive stiffness and strength showed good agreement with the measurements, and the failure mechanisms of the structures were discussed by simulation analysis.

      PubDate: 2017-10-11T01:48:13Z
       
  • Characterization of residual stress and deformation in additively
           manufactured ABS polymer and composite specimens
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Wei Zhang, Amanda S. Wu, Jessica Sun, Zhenzhen Quan, Bohong Gu, Baozhong Sun, Chase Cotton, Dirk Heider, Tsu-Wei Chou
      Residual stresses induced in the layer-by-layer fabrication process of additively manufactured parts have significant impact on their mechanical properties and dimensional accuracy. This work aims to characterize the residual stress and deformation in specimens based on unreinforced acrylonitrile-butadiene-styrene (ABS), carbon nanotube reinforced ABS and short carbon fiber reinforced ABS. The shrinkage and displacement fields were obtained, respectively, by thermal treatment as well as Digital Image Correlation observation of specimens before and after sectioning. The microstructure and porosity of additively manufactured specimens were also examined using X-ray micro-computed tomography. Specimen shrinkage and porosity content were significantly influenced by the process parameters of raster angle and printing speed, as well as material types. Faster printing speed led to larger porosity and residual stress, as well as higher shrinkage after specimen thermal treatment. Raster angle had a greater influence on specimen shrinkage and porosity as comparing to printing speed. Composite printing wires based on carbon nanotube and short carbon fiber in ABS greatly reduced specimen shrinkage and deformation, while increased the porosity, especially for carbon fiber reinforced ABS specimens.

      PubDate: 2017-10-11T01:48:13Z
       
  • Local surface mechanical properties of PDMS-silica nanocomposite probed
           with Intermodulation AFM
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): H. Huang, I. Dobryden, P.-A. Thorén, L. Ejenstam, J. Pan, M.L. Fielden, D.B. Haviland, P.M. Claesson
      The mechanical properties of polymeric nanocomposites are strongly affected by the nature of the interphase between filler and matrix, which can be controlled by means of surface chemistry. In this report, we utilize intermodulation atomic force microscopy (ImAFM) to probe local mechanical response with nanometer-scale resolution of poly(dimethylsiloxane) (PDMS) coatings with and without 20 wt% of hydrophobic silica nanoparticles. The data evaluation is carried out without inferring any contact mechanics model, and is thus model-independent. ImAFM imaging reveals a small but readily measurable inhomogeneous mechanical response of the pure PDMS surface layer. The analysis of energy dissipation measured with ImAFM showed a lowering of the viscous response due to the presence of the hydrophobic silica nanoparticles in the polymer matrix. An enhanced elastic response was also evident from the in-phase stiffness of the matrix, which was found to increase by a factor of 1.5 in presence of the nanoparticles. Analysis of dissipation energy and stiffness in the immediate vicinity of the nanoparticles provides an estimate of the interphase thickness. Because the local stiffness varies significantly near the nanoparticle, AFM height images contain artifacts that must be corrected in order to reveal the true surface topography. Without such a correction the AFM height images erroneously show that the stiff particles protrude from the surface, whereas corrected images show that they are actually embedded in the matrix and likely covered with a thin layer of polymer.

      PubDate: 2017-10-11T01:48:13Z
       
  • Effects of waviness on fiber-length distribution and interfacial shear
           strength of natural fibers reinforced composites
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Vito Gigante, Laura Aliotta, Vu Thanh Phuong, Maria Beatrice Coltelli, Patrizia Cinelli, Andrea Lazzeri
      Natural fibers are not as rigid as glass or carbon fibers. During composites extrusion and injection molding, they tend to bend and twist in the polymeric matrix, thus resulting in fiber waviness and decreased mechanical properties of natural fiber composites. The most widely used models for the estimation of interfacial shear strength (IFSS) and elastic modulus, which consider the fiber aspect ratio and mechanical properties of the fiber and matrix, do not consider these important features. In order to account for fiber waviness, an effective fiber length is proposed in this paper. The undulation of the fibers is approximated with a sinusoidal arc along with a calculated new length. The proposed correction factor depends on the wavelength and amplitude of the wave approximating the fiber. To verify this method, blends of polylactic acid (PLA) and polycarbonate (PC) (prepared with and without an interchange reactions catalyst) with addition to various percentages of cellulosic fibers (5 wt%, 10 wt% and 15 wt%) have been prepared and characterized. It has been demonstrated that by considering the corrected length values, it is possible to predict the mechanical properties and the effective reinforcement attained in the composites by using the most widely used models. In particular, the prediction of the elastic modulus is slightly affected by this correction, whereas the calculation of IFSS is strongly dependent on it.

      PubDate: 2017-10-04T07:18:12Z
       
  • Precise stimulation of near-infrared light responsive shape-memory polymer
           composites using upconversion particles with photothermal capability
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Liang Fang, Tianyu Fang, Xiaoxia Liu, Yaru Ni, Chunhua Lu, Zhongzi Xu
      The incorporation of thermally-induced shape-memory polymer (SMP) with photothermal fillers has been widely used in creating photoresponsive SMP composites (SMPCs). Near-infrared (NIR) light, which is safer for human tissues and naked eyes, has been widely used to trigger such intelligent SMPCs containing carbon nanomaterials, metal nanoparticles, or rare earth organic complexes. There is still a need to aim invisible NIR light beam remotely onto SMPCs to realize the precise shape recovery of their featured areas. Here, NaYF4:99.5%Yb3+, 0.5%Tm3+ particles presenting both upconversion and photothermal capabilities were utilized as multifunctional fillers in a crosslinked copolymer of methyl methacrylate and butyl acrylate, enabling the prepared SMPCs to transfer the NIR light at 980 nm simultaneously into both visible light and heat. The particles with a low content up to 1 phr did not vary the crosslinking level and glass transition temperature of the SMPC. With the aid of upconversion at a relatively low power density, the position of laser beam on SMPC surface was detected easily, facilitating the aim towards the area anticipated to be triggered without inducing a shape deformation. The subsequent increase in power density successfully resulted in the precise shape recovery with the recovery ratio higher than 90%. The concept of precise location before stimulation was demonstrated in the cases of multiple shape deformations, remote activation in the darkness, and microscale structured surfaces. The reported multifunctional nanoparticles truly executed the remote and precise trigger of SMPCs using invisible NIR light, which can be further exploited in other thermally-induced smart polymer composites.

      PubDate: 2017-10-04T07:18:12Z
       
  • Nanoscale evaluation of multi-layer interfacial mechanical properties of
           sisal fiber reinforced composites by nanoindentation technique
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Qian Li, Yan Li, Limin Zhou
      The multi-layer structure of plant fibers has been revealed qualitatively by qualitative microscopic characterization and associated with multi-stage failure behaviors of plant fiber reinforced epoxy composites. To quantitatively evaluate the nanoscopic mechanical properties of sisal fiber (a typical plant fiber) reinforced epoxy composites (SFRCs) involving the unique structural characteristics, elastic modulus and hardness of the epoxy matrix and cell wall layers of sisal fiber along with interfacial mechanical properties were measured by applying the nanoindentation technique. A series of indents were conducted at selected positions from the matrix to each layer of the fiber cell walls to ascertain transition zones of the multi-layer interfaces. Single-step and multi-step nanoindentation methods were respectively employed on the multi-layer interfaces of SFRCs to present their distinct mechanical properties in terms of modulus and hardness, energy dissipation, crack initiation and propagation upon compressive loading. This study measures the transition zones of the multi-layer interface and the interfacial failure load, which consequently facilitates a quantitative analysis of fracture mechanisms for SFRCs with a multi-scale and multi-layer structure.

      PubDate: 2017-10-04T07:18:12Z
       
  • High-order three-scale method for mechanical behavior analysis of
           composite structures with multiple periodic configurations
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Zihao Yang, Yang Zhang, Hao Dong, Junzhi Cui, Xiaofei Guan, Zhiqiang Yang
      A new high-order three-scale (HOTS) method for simulating the mechanical behaviors of composite material structures with multiple heterogeneities is developed. The heterogeneities of the structures are taken into account by periodic layouts of unit cells on the microscale and mesoscale. A novel unified micro-meso-macro multiscale formulation based on reiterated homogenization and multiscale asymptotic expansions is established successively. Two kinds of local cell functions defined on the mesoscale and microscale cells, including first- and second-order, are established. The equivalent material parameter is calculated by up-scaling procedure and homogenized problem is subsequently defined. Further, the displacement, strain and stress are constructed as multiscale asymptotic expansions by assembling the cell functions and homogenation solution. In the present method, both the mesoscopic and microscopic information are synthesized with homogenization solution to capture more local characteristics inside the composite material structures. Then, the finite element numerical algorithm based on the three-scale method is brought forward in details. Finally, numerical examples are given to demonstrate the usability of the HOTS analysis method to simulate the mechanical behavior. This study offers a unified multiscale framework that enables mechanical behavior analysis of composite structures with multiple spatial scales.

      PubDate: 2017-10-04T07:18:12Z
       
  • Enhanced microwave-absorption performance of FeCoB/Polyimide-Graphene
           composite by electric field modulation
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Zhenjun Xia, Jun He, Xiulong Ou, Yang Li, Yu Wang, Bin Shen, Xiang Yu, Shuli He, Dongliang Zhao, Guanghua Yu
      Graphene was incorporated into polyimide resin to obtain Polyimide-Graphene polymer sheet via in-situ polymerization method. FeCoB nanoparticles, generated by a high energetic cluster deposition system, were then deposited on the Polyimide-Graphene sheets by electric field assisted deposition technology to form FeCoB/Polyimide-Graphene ternary composites. An electric field of about 5–30 kV was applied on the sample platform when the composites were manufactured. The strong magnetic properties of the composites were revealed by the measurement of hysteresis loops at room temperature. Then the laminated FeCoB/Polyimide(-Graphene) composites were used to perform reflection loss scan. It is found that the addition of a small amount of graphene promote the improvement of electromagnetic properties by increasing dielectric loss. And the cover of FeCoB films can dramatically enhance the microwave absorption capacity by enriching interfacial polarization effect and electromagnetic match. The results prove that the electric field assisted deposition technique is a very attractive avenue to enhance the microwave absorption performance of the ternary composite expressed by tuning their dielectric and magnetic properties.

      PubDate: 2017-10-04T07:18:12Z
       
  • A novel Co(Ⅱ)–based metal-organic framework with phosphorus-containing
           structure: Build for enhancing fire safety of epoxy
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Yanbei Hou, Weizhao Hu, Zhou Gui, Yuan Hu
      Co–based metal-organic framework with phosphorus-containing structure (P-MOF) was synthesized by a facile hydrothermal reaction and was first added into epoxy resin (EP) to enhance its fire safety, including flame retardancy, toxicity reduction, and smoke suppression. It was found that the values of peak heat release rate and total heat release of EP were decreased by 28% and 18.6% respectively at 2 wt% content of P-MOF. Meanwhile, the notable reductions of total smoke production and total CO yield were also observed from results of cone calorimeter and the steady state tube furnace, decreased by 15% and 52% respectively. Due to the absorption and catalytic effect of P-MOF and its residues, the release of organic volatiles and CO generated during the pyrolysis process of EP was significantly suppressed. Based on the analysis of gas and condensed phase, the possible mechanism of the enhanced fire safety was proposed as the combination of the adsorption and catalytic effect of P-MOF, which provides a promising application of MOFs to enhance the fire safety of polymer materials.
      Graphical abstract image

      PubDate: 2017-10-04T07:18:12Z
       
  • Dense graphene foam and hexagonal boron nitride filled PDMS composites
           with high thermal conductivity and breakdown strength
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Haoming Fang, Xiao Zhang, Yunhong Zhao, Shu-Lin Bai
      In the present study, high thermally conductive and electrically insulated polymer composites containing modified dense graphene foam (MGF) and modified hexagonal boron nitride (M-h-BN) via polydopamine (PDA) coating and 3-aminopropyltriethoxysilane (APTS) grafting were manufactured and studied. Due to the double percolated networks built by MGF and M-h-BN, the polydimethylsiloxane (PDMS) matrix composite has high thermal conductivity of 23.45Wm−1K−1 and 2.11Wm−1K−1 in in-plane and out-of-plane directions, respectively. In addition, an insulated layer of M-h-BN/PDMS can be introduced onto both sides of composite sample with the help of infiltration technique, which results in a high breakdown strength of 4.5 kV/mm. Owing to the excellent comprehensive properties, the M-h-BN/MGF/PDMS composite has a promising application in heat management field of the microelectronic industry.

      PubDate: 2017-10-04T07:18:12Z
       
  • Phenolic resin-enhanced three-dimensional graphene aerogels and their
           epoxy nanocomposites with high mechanical and electromagnetic interference
           shielding performances
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Yu Chen, Hao-Bin Zhang, Mu Wang, Xin Qian, Aravind Dasari, Zhong-Zhen Yu
      Highly porous graphene aerogels enhanced with phenolic resol resin are prepared by a hydrothermal synthesis followed by high-temperature annealing. The introduced phenolic resol resin and its pyrolysis derivative effectively combine the sheets together and thus the three-dimensional networks of the enhanced aerogels are well retained even after compounding with epoxy resin. The synthesized aerogels are highly efficient in endowing epoxy with high electrical conductivity, excellent electromagnetic interference (EMI) shielding efficiency and satisfactory mechanical reinforcement. With only 0.33 wt% of the annealed aerogel, its epoxy nanocomposite exhibits a high electrical conductivity of 73 S/m and an excellent EMI shielding effectiveness of 35 dB, which are among the best results for polymer nanocomposites with even higher loadings. Especially, the EMI shielding performance is comparable to or even higher than that of the nanocomposite filled with chemical vapor deposition-synthesized graphene foam. Furthermore, the aerogel also leads to notable 67% and 20.2% increases in flexural strength and flexural modulus, respectively. Therefore, the phenolic resin-enhanced graphene aerogel holds a great potential in producing high-performance polymer nanocomposites for EMI shielding application.

      PubDate: 2017-10-04T07:18:12Z
       
  • Healing of a glass fibre reinforced composite with a disulphide containing
           organic-inorganic epoxy matrix
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): W. Post, A. Cohades, V. Michaud, S. van der Zwaag, S.J. Garcia
      We report the development of an intrinsic healing glass fibre reinforced polymer (GFRP) composite based on a disulphide-containing organic-inorganic thermoset matrix. Thermomechanical experiments showed that the newly developed matrix has a combination of a Young's modulus value in the range of (800–1200 MPa), the ability to multiple thermally induced healing delamination (70–85 °C), and processability by conventional vacuum infusion process that is not yet reported in literature. The composite mechanical properties and the extent of healing were determined by flexural, fracture and low-velocity impact testing. Small sized (<cm2) damage could be partially healed multiple times using a minimal healing pressure to ensure a good alignment of the damaged interfaces. The level of healing can be enhanced, even for large (>cm2) damage, by increasing the healing pressure provided the location of the primary damage is concentrated within the matrix phase. The polymer matrix composite introduced here represents a significant step forward from the often mechanically inferior intrinsically self-healing composites towards structural self-healing composites.

      PubDate: 2017-09-26T12:43:08Z
       
  • Highly flexible and stretchable thermally conductive composite film by
           polyurethane supported 3D networks of boron nitride
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Hye-Jin Hong, So Mang Kwan, Dong Su Lee, Seung Min Kim, Yun Ho Kim, Jin Seong Lim, Jun Yeon Hwang, Hyeon Su Jeong
      Current interest in flexible and stretchable electronics has been amplified because of their remarkable features for numerous applications. Accordingly, compliant efficient thermal management for such electronics is in great demand. However, new materials simultaneously coping with high thermal conductivity and mechanical flexibility have not been sufficiently studied. Here, we report a simple yet highly efficient method to construct three-dimensional (3D) hexagonal boron nitride (h-BN) network in a polymer composite, which is both thermally conductive and mechanically stretchable. 3D h-BN network is easily fabricated by in-situ incorporation of h-BN onto the surface of a water-borne polyurethane (PU) scaffold during polymerization. The 3D h-BN network in the composite film offers high thermal conductivity up to 10 W/m·K while the PU contributes excellent mechanical flexibility such as folding, twisting and stretching. Moreover, the process developed in this study is highly economical and processable to be scaled up without the need of complex equipment or procedure, which will be of great interest to current manufacturing as well as soft and stretchable electronic devices.
      Graphical abstract image

      PubDate: 2017-09-26T12:43:08Z
       
  • High performance quasi-isotropic thin-ply carbon/glass hybrid composites
           with pseudo-ductile behaviour in all fibre orientations
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Mohamad Fotouhi, Meisam Jalalvand, Michael R. Wisnom
      This study exploits the potential of thin-ply carbon/glass hybrid laminates to generate high performance Quasi-Isotropic (QI) composite plates that show pseudo-ductility in all fibre orientations under tensile loading, overcoming the inherent brittleness of conventional composites. Two types of QI lay-ups with 45° and 60° intervals, i.e. [45/90/-45/0] and [60/-60/0], were used to fabricate novel architectures of a QI T300-carbon laminate sandwiched between the two halves of a QI S-glass laminate. The fabricated plates were then loaded in all their fibre orientations. The laminates were designed by choosing an appropriate ratio of the carbon thickness to the laminate thickness using a robust analytical damage mode map. The experimental results verified the analytical predictions and showed a desirable pseudo-ductile failure in all the fibre orientations. Microscope images taken through the laminates thickness showed fragmentations (fibre fractures in the carbon layer) appearing only in the 0° carbon plies. A hybrid effect was observed, with an increase in strain and stress to failure of the carbon fibres, which was found to be dependent on the stiffness of the plies separating the 0° carbon plies and the plies adjacent to the 0° carbon plies. Altering the stacking sequence changes the stiffness of the separator and adjacent plies, therefore, leads to changes in the pseudo-ductile characteristics such as the initiation and final failure strains.

      PubDate: 2017-09-26T12:43:08Z
       
  • Tailoring co-continuous like morphology in blends with highly asymmetric
           composition by MWCNTs: Towards biodegradable high-performance electrical
           conductive poly(l-lactide)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate)
           blends
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Tao Gao, Yuan-Yuan Li, Rui-Ying Bao, Zheng-Ying Liu, Bang-Hu Xie, Ming-Bo Yang, Wei Yang
      The performance of polymer blends greatly depends on the phase morphologies and the incorporation of nanofillers provides a low-cost but efficient strategy to tailor the morphology and performance of immiscible polymer blends. In this work, we obtained co-continuous like morphology in poly(l-lactide) (PLLA)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) blend with highly asymmetric composition (80/20, wt/wt) through the self-networking behavior of multi-walled carbon nanotubes (MWCNTs). It was found that the electrical conductivity and the ductility of PLLA/P(3HB-co-4HB)/MWCNTs composites were enhanced at the same time compared with PLLA/MWCNTs composites. The percolation threshold of the prepared PLLA/P(3HB-co-4HB)/MWCNTs composites was 0.58 wt%, 36% lower than that of PLLA/MWCNTs composites and the highest value of elongation at break for PLLA/P(3HB-co-4HB)/MWCNTs composites was 226.4% when the content of MWCNTs was 1 wt%. The results indicate that MWCNTs can contribute to the formation of co-continuous like structure and our work provides a new way to prepare biodegradable high-performance conductive polymer composites with excellent conductivity and mechanical properties.

      PubDate: 2017-09-26T12:43:08Z
       
  • A micromechanical model of graphene-reinforced metal matrix nanocomposites
           with consideration of graphene orientations
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Chongyang Gao, Bin Zhan, Lianyi Chen, Xiaochun Li
      In this paper, a new micromechanical model is developed for graphene-reinforced metal matrix nanocomposites (MMNCs) to effectively describe the mechanical properties of the new attractive engineering materials with high specific strength. The key influence of the misorientation of randomly-distributed graphene nanoplatelets (GNPs) is especially considered. The strain rate and temperature effects are also introduced through the dislocation-mechanics-based metal matrix model. Then the new model is applied to the nanocomposites of GNP/Al2024, GNP/Al and GNP/Cu, respectively. The comparison of model predictions and experimental data suggests that the model can represent the elastoplastic deformation behaviors of the graphene-reinforced MMNCs well. The strengthening effect by graphene in the nanocomposites is approximately linear to its volume fraction within a small range and also to the aspect ratio of graphene platelets when their average length is less than a critical value. Moreover, the dynamic thermomechanical behavior of the GNP/Al2024 nanocomposite is predicted for the first time. The temperature-softening effect becomes weaker under dynamic loading conditions while the rate sensitivity would be enhanced at elevated temperatures.

      PubDate: 2017-09-26T12:43:08Z
       
  • Influence of water uptake on the electrical DC-conductivity of insulating
           LDPE/MgO nanocomposites
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Fritjof Nilsson, Mattias Karlsson, Love Pallon, Marco Giacinti, Richard T. Olsson, Davide Venturi, Ulf W. Gedde, Mikael S. Hedenqvist
      Low-density polyethylene (LDPE), typically in cross-linked form, is currently the main insulation material for extruded high voltage cables. The DC-conductivity of LDPE can be reduced 100 times by adding 1–3 wt% well-dispersed metal-oxide nanoparticles (MgO, ZnO, Al2O3), but the underlying physics remain unclear. One of several feasible explanations is that the nanoparticles attract electrical charges, polar molecules (H2O and crosslinking by-products) and ions (H+, OH−, salts and ionic species originating from the crosslinking by-products), and thus clean the polymer. Effective media FEM simulations, assuming that the polymer conductivity is proportional to the moisture content, were used in order to examine this hypothesis. Water sorption measurements for LDPE and MgO/LDPE nanocomposites were conducted as experimental input. The simulations could conceptually predict the experimentally measured composite conductivities. The hypothesis was further strengthened by DC-conductivity measurements on LDPE and MgO/LDPE nanocomposites at 0 and 50% relative humidity (RH), showing a 100-fold conductivity increase for the nanocomposite at the elevated humidity. The DC-conductivity of the most insulating composite (3 wt% MgO) was below 10−16 S/m after 64 h at 60 °C and 0% RH, using an electric field of ca 30 kV/mm. The long-term insulation efficiency of an insulating polymer nanocomposite is thus optimal if the material is carefully dried and surrounded by an impenetrable moisture barrier before use.

      PubDate: 2017-09-20T07:16:53Z
       
  • Preliminary demonstration of energy-efficient fabrication of aligned
           CNT-polymer nanocomposites using magnetic fields
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Jatin Haibat, Steven Ceneviva, Mychal P. Spencer, Frances Kwok, Shreya Trivedi, Suzanne E. Mohney, Namiko Yamamoto
      Preliminary fabrication of thermoset nanocomposites with aligned carbon nanotubes (CNTs) is demonstrated using magnetic fields in an energy-efficient and quick manner. Bulk application of high-performance polymer nanocomposites is currently limited because scalable manufacturing methods to deliver bulk samples with organized nanofillers are currently missing. In this work, active assembly using external magnetic fields is selected as a solution to provide the balanced benefits of bulk processing capacity and tailorable patterning capability. Magnetically-responsive multi-walled carbon nanotubes (∼35 nm diameter and ∼200 μm length) were fabricated with relatively simple post-growth processing: low-temperature oxygen plasma treatment for improved suspension and dispersion within matrices, and e-beam coating with thin ferromagnetic nickel (Ni) layers (∼40–100 nm) for larger magnetic susceptibility. Dispersion and properties of the plasma-treated and Ni-coated CNTs were evaluated visually using the settlement study and scanning electron microscopy, and quantitatively using Raman spectroscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Assembly of Ni-coated CNTs was first demonstrated in deionized water, and then in a bisphenol-F based polymer resin (Epon 862). Magnetic assembly behaviors of these two-dimensional nanofillers were studied about the effect of their original dispersion, size, and matrix viscosity. The first sizable fabrication of CNT-thermoset nanocomposite (∼32 mm × ∼32 mm × ∼5 mm sample size) was attempted and demonstrated with the smaller magnetic field in the shorter time (∼400 G application for 40 min), than the previous attempt to assemble CNTs (∼105 G for a few hours). Future work include homogenization of CNT patterns within the nanocomposites by improving the original CNT dispersion and suspension (ferromagnetic filling instead of coating, particle surface treatment, etc.), more complex CNT patterning using magnetic field parameter modulation, and structure-interface-property studies by polymer nanocomposite characterization, specially about transport properties.

      PubDate: 2017-09-20T07:16:53Z
       
  • Aligning carbon nanofibres in glass-fibre/epoxy composites to improve
           interlaminar toughness and crack-detection capability
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Shuying Wu, Raj B. Ladani, Anil R. Ravindran, Jin Zhang, Adrian P. Mouritz, Anthony J. Kinloch, Chun H. Wang
      An electric field is used to align carbon nanofibres (CNFs) in the matrix of a glass-fibre reinforced-polymer (GFRP) composite to simultaneously improve the (a) delamination toughness, (b) electrical conductivity, and (c) damage-sensing capability. The CNFs are added to the epoxy resin prior to the manufacture of the GFRP composites. To align the CNFs, an alternating current (AC) electric field of 30 V/mm at 10 kHz is applied across the GFRP sheet throughout the matrix-curing process. The electromechanical force induced by the electric field, applied in the through-thickness direction of the composite sheet, rotates and aligns the CNFs in the direction of the applied electric field prior to the gelation of the epoxy matrix. After curing, the resultant aligned, ‘chain-like’, microstructure of the CNFs in the epoxy matrix significantly enhances both the interlaminar fracture toughness and the through-thickness electrical conductivity of the GFRP composite. Specifically, the addition of 0.7 vol% of randomly-orientated CNFs in the GFRP composite yielded an ∼50% and 25% increase in the values of the mode I fracture toughness pertinent to the initiation, G Ici , and steady-state growth, G Icss , of delamination crack, respectively, compared to the control GFRP composite. The alignment of the CNFs, in the transverse direction to the direction of the crack growth, increases the mode I toughness values of G Ici and G Icss by ∼100% and ∼80%, respectively, compared to the control GFRP composite. These significant increases are attributable to multiple toughening mechanisms, including debonding of the CNFs from the matrix, void growth of the epoxy matrix, pull-out and rupture of the CNFs. Further, the electric-field induced alignment of the CNFs, in the through-thickness direction, increases the out-of-plane electrical conductivity of the GFRP by about twenty-six times, compared to the GFRP composite containing randomly-orientated CNFs. Of particular interest, the damage-sensing capacity is enhanced for the GFRP composite with aligned CNFs in the epoxy matrix, which stems from the greatly increased out-of-plane electrical conductivity, as confirmed by a modelling study. Therefore, this present work has identified a new strategy to develop GFRP composites with greatly improved delamination toughness, electrical conductivity, and higher crack-detection sensitivity.

      PubDate: 2017-09-20T07:16:53Z
       
  • A novel procedure to determine the cohesive law in DCB tests
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Ainhoa Arrese, Ana Boyano, Juan De Gracia, Faustino Mujika
      A novel method is presented for the determination of mode I cohesive law for the characterization of delamination in unidirectional carbon fiber reinforced polymer laminates. The energy release rate as a function of the crack advance is determined based on an analytical approach where the compliance variation of the specimen as crack advances is used in order to obtain the crack length for every pair of load and displacement data. Based on the same analytic approach, the crack tip opening displacement is determined as a function of the equivalent crack advance assuming that the Fracture Process Zone development is analogous to an equivalent crack advance Δa. These measurements are used to compute the Energy Release Rate and crack opening displacement from which a cohesive law is determined by numerical differentiation. This new method provides a simple way to obtain the mode I cohesive law using only the load and displacement data obtained from the testing machine, without any external displacement measurement technique and without any assumption of the form of the cohesive law.

      PubDate: 2017-09-20T07:16:53Z
       
  • Fatigue and failure mechanism in carbon fiber reinforced plastics/aluminum
           alloy single lap joint produced by electromagnetic riveting technique
    • Abstract: Publication date: 10 November 2017
      Source:Composites Science and Technology, Volume 152
      Author(s): Hao Jiang, Guangyao Li, Xu Zhang, Junjia Cui
      Electromagnetic riveting (EMR) process is suitable for composite joining due to small damage. In this paper, the EMR experiments were conducted to obtain the fatigue samples. Specimens with normalized driven head dimensions were tested to obtain the fatigue behaviors. The experimental results showed that the driven head dimensions had a remarkable effect on fatigue property. The fatigue life increased first and then decreased with the increasing of D/D 0 (D and D 0 are the diameters of rivet driven head and original shaft, respectively). The electromagnetic riveted specimens with D/D 0  = 1.5 had the best fatigue properties. The fatigue failure analysis showed that the specimens had three typical fatigue failure modes: failure in the rivet, failure in the Al sheet and failure in the CFRP and Al sheets as influenced by driven head dimensions and stress levels.

      PubDate: 2017-09-14T03:15:27Z
       
  • High electrochemical performances of solid nano-composite star polymer
           electrolytes enhanced by different carbon nanomaterials
    • Abstract: Publication date: Available online 13 September 2017
      Source:Composites Science and Technology
      Author(s): Ailian Wang, Hao Xu, Xu Liu, Shi Wang, Qian Zhou, Jie Chen, Liaoyun Zhang
      Here, two type of composite star polymer electrolytes enhanced by carbon nano-tube (CNT) or fullerene (C60) prepared through a solution-casting technique are investigated. The as-prepared free-standing carbon nano-composite polymer electrolyte membranes exhibit excellent comprehensive performances including high thermal stability (initial thermal degradation temperatures about 383 °C) and good electrochemical properties. However, different carbon nanomaterials bring different influence on electrochemical performances of composite polymer electrolytes. The ionic conductivity of carbon nanotube composite polymer electrolyte (HBPS-(PMMA-b-PPEGMA)30/CNT/LiTFSI) is higher than that of fullerene composite polymer electrolyte. The highest ionic conductivity of HBPS-(PMMA-b-PPEGMA)30/CNT/LiTFSI electrolyte can reach 1.06 × 10−5 S cm−1 at 30 °C and lithium-ion transference number reaches 0.52. In addition, two types of carbon nano-composite star polymer electrolytes both exhibit wide electrochemical window with oxidation potential of above 5.2 V, good interfacial stability and interfacial compatibility. Moreover, assembled Li/LiFePO4 cells based on HBPS-(PMMA-b-PPEGMA)30/CNT/LiTFSI electrolytes possess good specific capacity with the highest value of 133 mAhh g−1, while the cells based on HBPS-(PMMA-b-PPEGMA)30/C60/LiTFSI electrolytes show a great cycle stability.

      PubDate: 2017-09-14T03:15:27Z
       
  • Transverse permeability of dry fiber preforms manufactured by automated
           fiber placement
    • Abstract: Publication date: Available online 12 September 2017
      Source:Composites Science and Technology
      Author(s): A.R. Aziz, M.A. Ali, X. Zeng, R. Umer, P. Schubel, W.J. Cantwell
      This work presents a correlation between the transverse permeability of a preform and the process variability of the automated dry fiber placement manufacturing technique. In this study, an experimental and numerical analysis of the dry tape preform, with a focus on its through-thickness permeability, has been undertaken. Geometric models, containing flow channels of two different width dry tape carbon preforms, have been created in the TexGen modeller. A Computational fluid dynamics (CFD) simulation has been undertaken to obtain the predicted through-thickness-permeability of the dry tape preform. A parametric study on the effect of different dry tape gap sizes on the permeability of the preform is presented. An in-situ compaction study, carried out in an X-CT machine, revealed that the gap sizes were irregular throughout the manufactured preforms. In addition, an experimental investigation of the through-thickness permeability, which is based on a saturated flow condition at a thickness corresponding to full vacuum pressure, is also presented. The permeability prediction based on the X-CT re-constructed geometric model has been validated using the experimental data. A further parametric study has revealed that the process variablity in automated dry fibre placement influences the through-thickness permeability by a factor of upto 5.

      PubDate: 2017-09-14T03:15:27Z
       
  • Irreversible tunability of through-thickness electrical conductivity of
           polyaniline-based CFRP by de-doping
    • Abstract: Publication date: Available online 9 September 2017
      Source:Composites Science and Technology
      Author(s): Vipin Kumar, Tomohiro Yokozeki, Teruya Goto, Tatsuhiro Takahashi, Sanjay R. Dhakate, Bhanu P. Singh
      Carbon fiber reinforced plastics (CFRPs) are known for their tunable mechanical properties but not for having tunable electrical properties. In this work, a composite CFRP based on conductive polyaniline (CF/PANI) was prepared, which demonstrates electrical conductivity that is controllable post-fabrication. A thermosetting matrix of PANI doped with dodecylbenzenesulfonic acid (DBSA) and dispersed in cross-linking divinylbenzene (DVB) polymer was used to impregnate carbon-fiber fabric. The electrical and mechanical properties of the CF/PANI composite were measured. For the first time, it was shown that thermal de-doping in PANI can be used to control the electrical conductivity of a CFRP made with PANI-based thermosetting matrix. An average electrical conductivity of 1.35 S/cm in the through-thickness direction of the CF/PANI is reported, which can be irreversibly reduced to a desired value by thermal annealing. UV-Vis and FT-IR spectroscopy were used to evaluate the doping quantitatively. Images obtained from an optical microscope fitted with a heating plate system demonstrate the de-doping of PANI. The mechanical properties of the composites were measured after each thermal treatment cycle to determine any deterioration; the irreversible modification of the CF/PANI's electrical conductivity occurs without any degradation of the mechanical properties.

      PubDate: 2017-09-14T03:15:27Z
       
  • Enhanced thermal conductivity of photopolymerizable composites using
           surface modified hexagonal boron nitride fillers
    • Abstract: Publication date: Available online 9 September 2017
      Source:Composites Science and Technology
      Author(s): Nir Goldin, Hanna Dodiuk, Dan Lewitus
      The interest in photocurable polymers has risen greatly in the past few years, in part due to the additive manufacturing revolution. Still, their widespread use is hindered by various inherent physical properties, such as thermal insulation. This work is aimed towards the development of photopolymerizable polymer composites that are thermally conductive, while maintaining their photocurable characteristics. We developed photocurable acrylic-based photopolymer composites with hexagonal boron nitride (hBN) using the following method: pristine hBN underwent two chemical surface modifications, was added to the monomers, and the mixture then underwent radiation curing. The success of the synthesis was verified in two ways: FTIR and XPS analyses in which the formation of carbonyl groups at the surface of the treated hBN was tracked, as well as tracking the increase in the homogeneity of the pre-polymerized solution. The addition of a reaction accelerator (o-benzoic sulfimide) to the photoinitiator system allowed for an increase of conversion percentage from ∼60% to ∼95%, even with high hBN loadings. Thermal conductivity (measured via modulated differential scanning calorimetry (MDSC)) increased with respect to hBN content by more than 300% when using 35 wt% hBN. Young's modulus and viscosity increased with hBN content, while coefficient of thermal expansion (CTE) decreased. We have thus developed a photocurable monomer system that is thermally conductive and applicable in various radiation curing processes.

      PubDate: 2017-09-14T03:15:27Z
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.162.152.232
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016